The present invention relates to implantable electrical stimulation systems and, more particularly, relates to lead extension and adapter systems that may be used in conjunction with a leadless, implantable microstimulator.
A neurostimulator is a device that provides electrical stimulation to selected nerves in the body. One type of neurostimulator that has been developed in recent years is a tiny microstimulator known as a BION® microstimulator. Various embodiments and features of the BION microstimulator are disclosed, e.g., in U.S. Pat. Nos. 5,324,316; 5,405,367; 6,051,017; and in PCT Publications WO 98/37926; WO 98/43700 and WO 98/43701, each of which patents or publications are incorporated herein by reference.
A microstimulator may be implanted via a small incision and/or via endoscopic means. In one preferred embodiment, the microstimulator is leadless, having electrodes fashioned or formed into its case. A “lead” as used herein will refer to an elongate body that includes a conductor and an insulation covering the conductor. The lead can further include an electrode on one end of the lead and a connector on the other end of the lead. The term “electrode” will be used herein as that portion (including insulation portion) of a stimulating lead which contains an electrode contact or electrode contacts for delivering the electrical stimulation to a tissue.
A leadless microstimulator must be implanted next to the nerve or tissue that is to be stimulated, since the electrode contacts are placed directly on the microstimulator case. The small size of the microstimulator allows it to be placed through minimally invasive surgery.
In other applications, however, it is not possible to implant the microstimulator immediately next to the nerve or tissue to be stimulated. In such instances, a leaded BION microstimulator may be used. Some examples are shown in co-pending U.S. patent application Ser. No. 10/188,465, filed 2 Jul. 2002 and in U.S. patent application Ser. No. 10/178,011, filed 20 Jun. 2002. Both of these patent applications are incorporated herein by reference.
In some cases, a leadless microstimulator may need to be used for an application that requires a lead extension. In particular, use of a specific type of electrode may be desired because the electrode type and number of electrode contacts are optimized for a specific application.
One type of electrode known in the art is a cuff electrode. A cuff electrode encircles a target nerve fiber or bundle and offers the advantage of being effectively attached to the target fiber or bundle, which prevents the electrode from inadvertently moving away from the desired, target nerve. A variation of the cuff electrode is a semi-cuff electrode that wraps or contacts one side of a target nerve bundle. A semi-cuff electrode may have one or more electrode contacts and operate as a monopolar electrode, a bipolar electrode or as a tripolar electrode, among others.
It would be desirable, in certain applications, to use a leadless microstimulator and to connect this microstimulator to a specific type of leaded electrode, for instance, a tripolar, semi-cuff electrode.
What is needed, therefore, is a system for adapting a leadless microstimulator so that it may be used with an extension lead that is connected to a selected electrode, such as a tripolar, semi-cuff electrode.